1. Field of the Invention
The invention relates to a cast iron material with lamellar graphite formation. It further relates to a motor vehicle part made of the cast iron material.
2. The Prior Art
Other materials than those used for cylinder crankcases are used for cylinder heads and brake discs because, for the latter two components, the thermal conductivity is the critical magnitude, not the strength. This is why cast iron with a perlitic matrix predominates in the case of cylinder crankcases, whereas predominantly ferritic cast iron with vermicular graphite is found in cylinder heads and a ferritic matrix in brake discs.
It is known practice to alloy ordinary cast iron with an addition of aluminium in order to reduce the density to a value below 7.2 g/cm3. This reduces the weight of the component and serves the purpose of light-weight construction. It is also known that cast iron alloyed with aluminium exhibits scaling resistance, meaning that an oxide layer adhering firmly to the surface of the component reduces wear under temperature load. This oxide layer also prevents the formation of flash rust at room temperature, which is undesirable in practice. Especially in the case of brake discs, flash rust is unattractive on a vehicle up for sale.